Allow all schemas to fall back to a string value

[luandy64]

Description of change

This PR changes discovery to write an anyOf schema for all fields.

Manual QA steps

• Made a sheet where a column gets a date-time schema, but some row after the first has a string instead of a date
• Made a sheet where a column gets a time schema
  • We currently output times like "123 days, 12:34:56"
• Made a sheet where a column gets a date-time schema, but some row after the first has a null cell

On master, the tap fails with transform errors for the first two test cases. On this branch, there are no transform errors and the records emitted have string values as expected.

On this branch, for the null cell test case, no transform error occurs and a null is emitted as expected.

Risks

• For tap runs that were previously encountering a transform error, this PR will likely cause a column split in downstream systems.
• For tap runs that were succeeding before, there should be no change.

Rollback steps

• revert this branch and bump the version

[KAllan357]

I think the anyOf should be on the specific date/time schema portions instead of applied to all. When its applied to them all, you'd end up with funny schema like anyOf: [null string], [null, string]